The control of bleeding during surgery accounts for a major portion of the time involved in an operation. In particular, bleeding that occurs when tissue is incised obscures the surgeon's vision, delays the operation, and reduces the precision of cutting.
One technique for minimizing the bleeding of tissue as it is being severed is known as hemostatic surgery. This technique uses a heated instrument to contact bleeding tissue. The heat is transferred from the instrument to the incised (or torn) tissue to reform thermally collagen, thereby producing a thin collagenous film that seals over the severed blood vessels and capillaries, thereby reducing bleeding. Because heat is applied locally to tissue that contacts the heated region of the instrument, there is little tissue necrosis or damage that, if present, would retard healing.
One such hemostatic instrument is known as a hemostatic surgical scalpel. This scalpel has a sharp cutting edge similar to that of a conventional steel scalpel blade, and a heating element proximate to the cutting edge to heat the blade. During cutting, the scalpel blade is heated and the heat is transferred to the tissue being cut.
One commercial device using this technique is the Shaw Hemostatic Scalpel, manufactured and sold by the Hemostatic Surgery Corporation, San Francisco, Calif., and described in U.S. Pat. Nos. 3,768,482, 30,190, 4,481,057, and 4,485,810. This device uses a multi-segmented resistive heating element whereby the current flowing through each segment is individually controlled to maintain each segment, and hence the blade, within a narrow range of user-selected temperatures.
A drawback of previously known hemostatic heated scalpel blades has been the inability to deliver an adequate quantity of heat in close proximity to the cutting edge, to maintain a sharp durable cutting edge, and to be usable for sustained surgery under a wide variety of surgical cutting applications. Sufficient thermal delivery is critical to seal promptly the blood vessels and capillaries being severed. The quantity of heat that must be delivered increases with the rate at which the scalpel is being moved through the tissue and the degree of vascularization of the tissue. These conditions have limited the cutting rate and depth that the previously known devices can be used to hemostatically cut tissue.
Good surgical blades are commonly made of hard materials such as steels and martensitic stain less steels, but these materials generally have low thermal conductivity. High thermal conductivity materials are desirable for delivering the necessary heat, but typically do not maintain a sharp and durable cutting edge. Contact of the high thermal conductivity blades with the corrosive biological fluids and operation at elevated temperatures combine to dull the cutting edges of such blades prematurely. Moreover, they also conduct large amounts of heat to the handle of the blade, making it uncomfortable for the surgeon to hold the instrument during surgery.
Attempts to use other blade materials have been made without any apparent success, e.g., ceramic blades as described in Shaw U.S. Pat. No. 3,768,482, Johnson U.S. Pat. No. 4,219,025, Lipp U.S. Pat. No. 4,231,371, and high thermal conductivity materials treated to have hardened cutting edges as described in U.S. Pat. No. 4,770,067. These devices similarly lack the combination of desirable thermal transfer properties and a durable sharp cutting edge.
Other types of hemostatic scalpel devices having non-segmented heating elements for heating the sharp scalpel blades are described in U.S. Pat. Nos. 4,207,896, 4,091,813 and 4,185,632.
Accordingly, there is a continuing need to provide a sharp, durable scalpel blade capable of delivering sufficient thermal energy to the tissue to cause hemostasis under a wide variety of operating conditions.